An ordinary computer system configured to diagnose a main memory, to detect a bad area in each of memory blocks into which an area of the main memory is divided by a certain length, and to identify a memory block in which a bad area is detected as a bad block is known, e.g., as disclosed in Patent document 1 and Patent Document 2.    [Patent Document 1]    Japanese Laid-open Patent Publication No. 05-37969    [Patent Document 2]    Japanese Laid-open Patent Publication No. 05-20207
The computer system of this kind is configured not to allow use of an identified bad block, and to use a normal memory block only other than the bad block in the main memory.
As the computer system does not use a bad block at all, generally, however, the computer system may not effectively use the whole main memory.